Chromosomal changes in relation to tumorigenicity of the murine L1210 leukemia line.

A spontaneous loss of tumorigenicity was observed in long-term in vitro culture of the cell line L1210(VAII), which was derived from mouse lymphoblastic leukemia L1210(V) of DBA/2 mice. The loss of tumorigenicity required at least 12 months of in vitro culture and was accompanied by the appearance of a new karyotypically distinct population. The dominant cell variant of the in vitro population that lost tumorigenicity showed duplication of a fragment within the M2 marker chromosome. The loss of tumorigenicity could be interpreted as a dose effect on tumor growth control by gene(s) localized within this marker chromosome.